Vegetable producers say they are already seeing signs of heat damage in their crop from a heatwave in southern Australia this week.

Emma Sykes

Vegetable producers say the extent of crop damage from this week's heatwave in southern Australia won't be known for weeks.

John Said, the chief executive officer of Fresh Select, one of the country's largest vegetable producers, says they've already seen burnt leaves and rapid growth in lettuce and broccoli crops at farms west of Melbourne and in Victoria's Gippsland region.

He says so far the damage hasn't been too severe, but the full extent won't be known for a number of weeks.

"It's generally a week to two weeks later when it starts to cool down and crops start to grow back into their normal sort of time that you actually see the effects.

"It could be three weeks, it could be four weeks ahead, it could have affected younger plants more than it's affected mature plants."

Mr Said says in the short term the company is taking measures to keep vegetables alive.

"It's simply just to keep our crops irrigated, keep our soils nice and wet, just try and give the crops as much nutrition and as much water as we possibly can, so they at least can survive and not dehydrate."

And in the longer term, he says, they are looking to varieties of plants that are better suited to hot weather.

"We are seeing that each summer period that we grow in gets hotter. It's as simple as that.

"We're trying to get varieties that are more tolerable to the heat, and we are trying to get varieties that grow in a certain time so they build a bit of resistance through the heat.

"The challenge is the peaks and the troughs that we experience."

Strawberry growers in Victoria are urging the public for support as they suffer from the blast of heat hitting the state.

The Victorian Strawberry Association says production for some growers is likely to be affected, which could see a drop in quality at a retail level.

“All I can say to the consumer is the strawberry, or any other industry at this time of year, needs people to keep buying and have a little faith in us, because it’s out of our control,” said the Association’s president Sam Violi.

A grower in Coldstream, east of Melbourne Mr Violi says although sunlight helps to develop sugars in strawberries, too much too quickly can ruin the development of the fruit.

“With the extra heat, you’re probably not getting the right balance of sugars,” he said.

“I think maybe the growers are not realising that the plant is so heat-stressed that the actual fruit is not ripening up naturally, what we call ‘forced ripening', and the quality will drop.”

Dairy Australia's animal health program manager Kathryn Davis says dairy cows are sensitive to high temperatures, which can lead to a reduction in their milk production.

"A cow that is quite stressed by high temperatures can even stop making milk altogether, but usually we just see a dropping off in the milk that they are making."

She says farmers in areas affected by the heatwave are providing their herds with more shade and cool water, and giving them showers under sprinkler systems.

"A lot of farmers will actually adapt their milking routine to work around the heatwave. They'll milk them very early, or much later at night when it's much cooler, so we are not expecting the cows to be out in the heat of the day."